The present invention relates to an image forming apparatus which comprises an image forming unit for forming images on a photosensitive material by exposing the material to light and an automatic developing unit disposed adjacent to the image forming unit for developing the images formed.
So-called home laboratory systems are known which comprise an automatic developing unit and an image forming unit disposed adjacent to the unit.
The automatic developing unit for treating materials sensitized with a silver salt produces chemical-containing vapors since chemical solutions are heated at a high temperature of at least 30.degree. C. for the developing process to achieve a high processing speed. It is desirable to prevent the release of these vapors to the ambient atmosphere in view of environmental hygiene and prevention of corrosion of the devices.
With the home laboratory system, therefore, the automatic developing unit has a cover provided over the development processing chambers therein, or an exhaust device provided in the space above the chambers thus covered.
However, the chemical-containing vapors produced within the developing unit are not always fully discharged into the upper space of the unit since this space communicates with the image forming unit through an inlet opening for receiving therethrough the photosensitive material from the image forming unit. The chemical-containing vapors remaining in the space are also likely to flow into the image forming unit owing to insufficient discharge of the vapors. It is further likely that the vapors will be drawn into the image forming unit from the upper space owing to temporary suction produced when the internal temperature of the image forming unit drops or when the door of this unit is opened outward.
These phenomena cause corrosion to some components of the image forming unit and impair its function. The unit, even if corroded slightly, would not function properly when designed as a precision machine for forming images on a photosensitive material by causing a laser beam to scan in the direction perpendicular to the direction of transport of the material.
The inlet opening for the photosensitive material is generally provided with a pair of transport rollers in pressing contact with each other and is substantially closed with these rollers which are in direct contact with each other or in intimate contact with the photosensitive material nipped therebetween. Nevertheless, no means is provided for sealing off the clearance in the inlet opening around the pair of rollers, while when a photosensitive sheet of small width is passed between the transport rollers, a clearance is inevitably generated between the rollers at the end portion. Consequently, it is impossible to completely prevent the flow of chemical-containing vapors into the image forming unit. This imposes a limitation on the width of photosensitive sheets usable.